While there are several lovely Australians on this board you might want to be a bit more specific about what your situation is if you want a reply.
Is a 4 year old ready for grade one typically or is your son advanced? (For instance -- grade one in America is usually for 6 year olds.)
And, if your son is academically advanced, is he mature enough for grade one?
And, "the right school" could mean anything. What do you mean by "the right school"?
If you are a bit more specific some of us might be able to help you.